1. Field of the Invention
The present invention relates to disinfection apparatus for use in connection with water treatment plants and involves the use of ultraviolet light for inactivating microorganisms. More particularly, the present invention relates to an improved ultraviolet-light-based disinfection reactor for treating water and that utilizes medium pressure ultraviolet lamps for microorganism treatment, either alone or as supplemented by a chemical oxidation treatment that can be included within the apparatus.
2. Description of the Related Art
Ultraviolet-light-based apparatus for disinfecting water by subjecting the water to ultraviolet light to inactivate microorganisms has been known for some time. Recently, several different forms of ultraviolet-based apparatus have been disclosed for the purpose of providing improved disinfection performance. Among those devices is one disclosed in U.S. Pat. No. 6,015,229, entitled “Method And Apparatus For Improved Mixing In Fluids,” which issued in Jan. 18, 2000, to Cormack et al. The Cormack et al. '229 patent discloses an array of tubular ultraviolet lamps that have their axes aligned with the flow direction to provide channels therebetween through which the fluid to be treated flows. Adjacent the upstream ends of the lamps are mixing devices in the form of triangular elements that create counter-rotating vortices that promote turbulent mixing of the fluid to increase the exposure time of the fluid to the ultraviolet light. However, the structure disclosed in the Cormack et al. '229 patent requires a lengthy treatment system, because of the alignment of the tubular lamps with the flow, that limits the adaptability of that arrangement as a retrofit for existing treatment plants, and it also utilizes a large number of ultraviolet lamps, which increases both the initial cost as well as the operating costs for such a system.
Other prior art arrangements orient the tubular lamps so that their axes are disposed perpendicular to the flow direction. Such arrangements are disclosed in U.S. Pat. No. 5,200,156, entitled “Device for Irradiating Flowing Liquids and/or Gases with UV Light,” which issued on Apr. 6, 1993, to Wedekamp, and U.S. Pat. No. 5,503,800, entitled “Ultra-Violet Sterilizing System for Waste Water,” which issued on Apr. 2, 1996, to Free. However, the Wedekamp '156 arrangement utilizes lamps that have a substantially rectangular cross section, with at least one pair of parallel sides, within either a constant cross-sectional area flow channel, or a flow channel that includes a diverging inlet section that defines an inlet diffuser, followed by a constant area center housing portion containing the lamps, and a converging outlet section. That arrangement also involves a lengthy treatment system that is difficult to incorporate as a retrofit for an existing water treatment system.
The Free '800 patent shows an arrangement in which elongate wall members are positioned on opposite sides of tubular lamps to define uniform width flow channels in which projections are provided on the wall members to induce turbulence of the liquid as it passes around the lamps. The Free '800 apparatus is intended for use in waste water treatment systems, in which the transmittance of the water is of the order of only about 20%, and thus especially narrow confinement of the untreated water about the lamp tubes is necessary, thereby reducing the effective flow throughput in such arrangements.
It is therefore desirable to provide an ultraviolet-light-based disinfection reactor that is of a more compact size and that is therefore adaptable for retrofitting into existing water treatment systems.